Numerous force accumulators are already known that make possible abrupt rotation of the driven shaft in that one or more loaded force accumulator springs are abruptly released. Such force accumulator springs can be not only tension springs, but also compression springs. The principle is in that case always the same: a rotating drive shaft loads the spring or the springs up to a maximum point and thereafter these abruptly relax and thereby move the driven shaft. Such a force accumulator is known from DE 10 2006 008 338 (US 20090000927 and U.S. Pat. No. 8,119,939) of Albrecht. Obviously, in the case of the force accumulators of that kind—as a consequence also of the spring characteristic—the torque is greatest at the commencement of triggering of the springs loaded until then; it decreases until the end position. However, in certain cases this predetermined course of torque, which is dependent on the spring characteristic as well as the respective kinematics, and the speed, which results therefrom, of the driven shaft is not desired. This particularly is true in cases in which a greater number of switching elements or other components of the on-load tap changer are to be actuated in succession in a specific sequence.
In such instances of use a force accumulator is therefore desirable in which a selective adaptation of the movement of the driven shaft to the respective actual requirements is achieved.
It is already known from DE-AS 25 02 810 to provide for that purpose an auxiliary force accumulator along with a force accumulator of the kind described above. Apart from the actual force accumulator springs a further spring is then provided which on triggering of the force accumulator is loaded by a toggle joint. In that case a deceleration of the triggered force accumulator in the first part of the movement course is achieved by this additional spring being loaded, whereas toward the end of travel, if the actual force accumulator spring is already largely relaxed, the additional spring is similarly relaxed so that the spring forces are cumulative. This known solution was conceived at the time in order to slow down the triggering of the force accumulator specifically for the purpose of being able to switch an alternating current of 16⅔ Hz instead of the usual alternating current at a frequency of 50 Hz without the switchover process as a whole elapsing too rapidly. This known force accumulator is, moreover, of mechanically complicated construction, particularly due to the roller guidance and additional toggle lever arrangement for actuation of the auxiliary force accumulator springs. Moreover, it is exclusively provided for a force accumulator in which a rotation of the drive shaft is initially converted into a longitudinal movement in which the force accumulator springs are loaded and the rapid longitudinal movement after triggering thereof is converted back into rotation of the driven shaft. The known solution is not suitable for direct conversion of continuous into rapid rotation.